make-flight: Add a single test with restricted dm

make-flight: Add a single test with restricted dm

As of this commit, this test is only functional: we don't do any
auditing yet.

Right now save/restore migration is broken with restricted dm, so
disable that test with the recipe flag.  See
  sg-run-job: Allow flight to specify recipe flag to disable migr tests

Run this only on recent enough Xen: the dm_restrict option was added
as an experimental feature in Xen 4.10 (currently as yet unreleased).
(With older libxl/xl, the option would be ignored and the test would
be a waste of time.)

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>